New Delhi, Jun 23 (IANS): While knowledge about how Covid-19 impacts different populations is still evolving, research so far has revealed that certain factors like age, diabetes, heart disease, high blood pressure, obesity, genetic factors and even blood type can influence the severity of the outcome.

According to the US Centers for Disease Control and Prevention (CDC), older adults and people who have severe underlying medical conditions like heart or lung disease or diabetes appear to be at greater risk for developing more serious complications from Covid-19 illness.

In fact, in the US, 8 out of 10 deaths reported have been in adults 65 years old and older, according to the CDC.

The American Heart Association also warned that those with conditions that affect the cardiovascular system, such as heart disease and hypertension, are at greater risk of worse outcome due to Covid-19 complications than those with no preexisting conditions, Live Science reported.

A study published in the journal Clinical Infectious Diseases said that obesity in Covid-19 patients younger than 60 years is a risk factor for hospital admission.

Another study published as a preprint online in the journal The Lancet Infectious Diseases, also found that obesity, especially in men, significantly increases the risk of developing severe pneumonia in Covid-19 patients.

However, it is not clear why obesity can increase risk of severe outcome, although it is generally believed that higher body mass index could be a risk factor for severe infection.

A study even found that people with blood group 'A' may be more prone to Covid-19 infection while those with blood type 'O' have a lower risk of contracting the virus.

For the study, researchers led by Wang Xinghuan with the Centre for Evidence-Based and Translational Medicine at Zhongnan Hospital of Wuhan University looked at blood group patterns of more than 2,000 infected patients in Wuhan and Shenzhen.

Scientists believe that certain genetic factors can also influence the risk of severe outcome.

As reported by Live Science, while certain combinations of human leukocyte antigen (HLA) genes which train immune cells to recognise germs may safeguard people against Covid-19, other combinations may make them more vulnerable, according to a study published in the Journal of Virology.